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When you’re first learning how to build a PC, everything can seem super complicated, but one of the most confusing things you’ll come across is motherboard size. Depending on what type of case you’ve purchased for your rig (and what type of hardware you want to put in your computer in general), you may have a ton of different size options. Below, I’ll go over all of the major iterations of modern motherboards and what they mean.
Want to learn more about gaming gear or PCs? Be sure to check out our guides on the best gaming keyboards, best gaming mice, best gaming headsets, and best gaming controllers.
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What is ATX?
Have you ever wondered why most modern computer motherboards look the same? That’s because almost all of them use ATX, a standard for motherboards, power supplies, and desktop cases that defines size, position, and power delivery. This set of rules helps all components work together, regardless of manufacturer.
For our purposes, we’re interested in physical dimensions. Some elements, such as the size and placement of ports on the back, are consistent across all ATX variants. Other aspects of the standard, such as board width and length, are indicated by their own acronyms, helping to quickly identify size and compatibility.
ATX Only
Photography: Amazon
ATX is the name of the standard and also the most common size. If you’ve ever opened the side of a computer case, you’re probably familiar with this form factor. Measuring 305 x 244 mm (12 x 9.6 inches), this motherboard has plenty of room for four or more RAM slots, multiple PCIe cards of various lengths, and two to four M.2 slots.
For example: ASUS TUF Gaming B650-Plus WiFi ($200) is a full-size ATX motherboard for the AMD AM5 platform. It features four RAM slots, two M.2 slots, and one PCIe 5.0 slot.
They’re a great choice for virtually any build, from the humble living room email checker to a powerful gaming rig. They’re usually the first to be released when a new generation is released, and have all the new features and options without paying a premium price. You don’t need a fancy computer to appreciate the benefits, as ATX motherboards also come in the widest variety of budgets and feature sets.
Micro ATX
Photography: Amazon
A slightly smaller option, micro ATX (or mATX for short) is becoming more and more common, thanks to constantly improving power and thermal efficiency. These boards are the same width as full-size boards, but are shortened at one end to be a square 244 x 244 mm. You’ll also find many of the same options and features you can find on ATX boards, without too big of a price increase, making them a popular choice for mid-range gaming PCs.
For example: The reasonable price MSI Pro B760M-P ($99) It has the CPU slot for the latest generation of Intel chips, a PCIe 4.0 slot, and only one M.2 slot.